The present invention relates to a method and corresponding apparatus for detecting objects via echoes. The present invention is a process, inspired by dolphins, for making images from echoes. The process is designed to be implemented in computer software but also suggests a compatible geometric arrangement of sensors which may be used in any number of applications. The process, with appropriate adjustments in sensor geometry, can image either telescopically or microscopically.
Most commercial products known in the art for making images from echoes rely on echoes produced by transmitted signals, or “clicks,” each of which travels to an echoing object down a path which is narrow in at least one of the two-dimensions of its cross sections; so, the path is either a narrow cone or a narrow fan (e.g. in sonar, an angle of one degree). The angle of a beam and the time of arrival of an echo combine to produce a point in an image. The full image might, thus, require a large multitude of transmitted clicks. By contrast, the present invention utilizes a computer and can make a 3-dimensional image-model from as few as one brief click which can have a broad beam (e.g. can be a cone whose angle of opening is approximately 15 degrees). The angle of the beam can be greater, as there is more computing power, or smaller should the expected environment have more noise.
Another distinguishing aspect of this work is that it uses time-instant based, rather than time-interval based, diffuse methods of analyzing signals and uses these instance-based methods in conjunction with sets of sensors (herein called “scopions”) which output sets of signals. Properties of the sets of signals are created, which properties relate to specific points in space.
Prior art (notably in radar) includes instances of a single-transmitter combined with a set of receivers. The new art here is distinguished by how a set of signals from a set of receivers is processed. Prior art uses various forms of time-interval-based, or “diffuse,” methods such as found in Fourier analysis and in statistics, correlation for example, while, such methods are absent here.
U.S. Pat. No. 5,090,245 describes a device which uses a single, broad beam insonifying signal and a multitude of sensors of “ultrasonic” echoes. The signal processing described or referred to in that patent seems to be “diffuse” and not at all of the time-instant form claimed herein. Further, that patent seems to totally miss the possibility of imaging via non-ultrasonic sound. Methods claimed herein can be used up to a range of several miles or more to image large, distant objects via a click whose “period” corresponds to “infrasound,” a sound frequency too low for humans to hear.
A ubiquitous thread in this Description is time-constraint. Few applications would be worth the amount of computer time which would be demanded by unlimited application of all the methods claimed herein. This set of methods is sufficiently rich that they can be selected among, some being emphasized more than others, as time and target-situation allow and demand.
Another thread is phantom reduction. The new methods here involve separating “real” associations from the false among signals from several sensors. The false associations might easily greatly outnumber the real. The present invention may also utilize code, exemplifying the methods claimed herein, which rapidly finds most true associations while avoiding, or detecting and eliminating, most phantoms.